This is the north most end of Nine Gun Battery. The focus was set on the close side of the stairs, so the background is not as sharp as it could be. Nine Gun battery is about 1,300 feet long, if you want to see the rest of it take a look at
http://www.gigapan.org/gigapans/18344/
Built between 1898 and 1904, three 8” and six 12” guns were used to protect New York Harbor. The battery was decommissioned 1943-44. The observation deck is visible in the top left, to see the view from the deck see
http://www.gigapan.org/gigapans/39977/